Interesting point. The Bible never records Yeshua/Jesus celebrating His birthday but we do have record of Him celebrating the Feasts, including Hanukkah!
Of course he celebrated his birthday...all Israel did. He was born on the first day of Sukkot (Feast of Tabernacles), a Sabbath and circumcised the eighth day, also a Sabbath.
If you count back 9 months from Sukkot you will be at Channuka...Yeshua then, would have been conceived at that time.